Hepatitis D (
hepatitis delta) is a
disease caused by the
hepatitis D virus (
HDV), a small circular enveloped
RNA virus. This is one of five known
hepatitis viruses:
A,
B,
C, D, and
E. HDV is considered to be a
subviral satellite because it can propagate only in the presence of the
hepatitis B virus (HBV). Transmission of HDV can occur either via simultaneous infection with HBV (
coinfection) or superimposed on chronic hepatitis B or hepatitis B carrier state (
superinfection).